FIG. 10 of the accompanying drawings illustrates a conventional trigger-type liquid dispenser or ejector to be fitted to an opening of a liquid container for exhausting or ejecting the liquid content in the container, where a tilted pump section A is arranged between a vertically disposed dispenser main body B and a horizontally disposed exhausting section C to allow a piston section D to have a sufficient stroke so that the liquid content in the container may be exhausted by a large amount in a single stroke. When, however, the dispenser is made of synthetic resin, it requires a cumbersome operation of being three-dimensionally released from a mold in X-, Y- and Z-directions, entailing necessarily the problem of the low productivity.
U.S. Pat. No. 4,819,835 discloses an improved dispenser for solving the problem of the low productivity.
FIG. 8 of the accompanying drawings schematically illustrates a trigger-type liquid dispenser disclosed in the U.S. Pat. No. 4,819,835. It includes a pump section E and an exhausting section F arranged horizontally and in parallel with each other so that the operation of releasing the molded product from the mold may be carried out only two-dimensionally in X- and Y-directions to raise the manufacturing efficiency.
However, since the pump section E is arranged horizontally, a stroke of a piston section G of the dispenser is reduced so as to reduce an amount of liquid that can be exhausted by a single stroke of the piston section G when compared with the dispenser of FIG. 10. In order to avoid the exhausted amount is reduced, the U.S. Patent discloses to use a cylinder H having a large diameter and a piston I having a large diameter so that the dispenser may exhaust a desired amount of liquid in as single stroke of the piston.
The trigger-type liquid dispenser illustrated in FIG. 8 also includes a container fitting section 1 and is rigidly fitted to the opening of a liquid container at the container fitting section 1. When a trigger 2 is pushed along the direction of arrow J, a press member 3 presses a horizontal groove 5 cut along a lateral side of a head 4 of a piston section G to displace piston I until its end surface 6 abuts a bottom wall 7 of a cylinder H. Thus, liquid contained in a cylinder chamber 8 is flowed out through a liquid inlet/output port 9 into a liquid path 10 so as to press a discharge valve body 11.
Then, the discharge valve body 11 is moved upwardly by the resilience of an elastic section 12 of the discharging valve body 11 to open a discharging valve seat 13. Thus, the fluid flows out from a discharging valve chamber 14 into a flow path 15 and then into other flow paths 16 and 17 so that it is finally exhausted or discharged through a nozzle 18.
Meanwhile, the piston I compresses a spring 19 contained therein, while the liquid in the liquid path 10 presses a ball valve 20 against a suction valve seat 21.
When the liquid is completely exhausted through the nozzle 18 and the trigger 2 is released, the piston I is returned to the position as shown in FIG. 8 by a resilient force of the spring 19. Thus, the cylinder chamber 8 is enlarged so as to decrease a pressure in the chamber 8. Since such negative pressure in the cylinder chamber 8 acts on the discharge valve body 11 and the ball valve 20, the discharge valve body 11 comes into contact with the discharge valve seat 13 to close the valve seat 13 and the ball valve 20 moves away from the suction valve seat 21 so that the liquid contained in the liquid container is drawn into the cylinder chamber 8 via a suction pipe 22, the liquid path 10 and the port 9 and stored there for the next exhausting operation.
An air intake port 23 is provided on a peripheral wall of said cylinder H and communicates with an inside of the liquid container, to which the container fitting section 1 is fitted, by way of air passages 24 and 25.
Said piston I is provided with an annular skirt 26 extending at an approach side (or the bottom wall 7 side of the cylinder H) and an annular skirt 27 extending at a stroke end (or an open end side of the cylinder H). The annular skirts 26, 27 are held in close contact with the inner wall surface of the cylinder H.
When the surface 6 of the approach end of said piston I abuts the bottom wall 7 of the cylinder H, a front edge 28 of the annular skirt 27 of the stroke end of said piston I is located closer to the bottom wall 7 of the cylinder H than the air port 23 of the cylinder. In such a case, the air intake port 23 communicates with an opening 29 of the cylinder H, and an air is introduced into the liquid container. On the other hand, when the piston I is located at the stroke end position as shown in FIG. 8, the air intake port 23 is located between the two annular skirts 26 and 27 and thus closed, so that the content of the liquid container may not flow out through the air intake port 23 if the liquid container is inadvertently turned upside down.
The above described trigger-type liquid dispenser disclosed in U.S. Pat. No. 4,819,835 can satisfactorily exhaust liquid so long as a user operates the trigger properly and the piston I is fully moved from the stroke end to the approach end of the piston I.
However, if the user repeatedly moves the trigger 2 by only a short stroke in an attempt to exhaust liquid at a reduced rate, the piston I is found in a position as illustrated in cross section in FIG. 9. Since the air intake port 23 of the cylinder H is located between the two annular skirts 26 and 27, the port 23 remains closed so that no air is allowed to flow into the liquid container, while the content of the liquid container is forced out repeatedly.
Thus, the pressure in the container is significantly reduced and the container would eventually be collapsed by atmospheric pressure.